Insect repellent



Patented Feb. 24, 1942 INSECT REPELLENT Philip Granett, New Brunswick,N. 1., assignor to National Carbon Company, Inc., a corporation of NewYork No Drawing. Original application June 4, 1938,

Serial No. 211,819. Divided and this application March 18, 1941, SerialNo. 383,921. "In Canada March 4, 1937 7 Claims.

Preparations capable of repelling mosquitoes, flies, gnats, fleas andother insect pests are genuinely valuable in the promotion of health andcomfort. This invention is concerned with insect repellents, and itsprimary object is to provide compositions of improved effectiveness inrepelling various insect pests, particularly mosquitoes.

I have found by test that insect repellent compositions of unusualefiicacy can be made by employing as their essential ingredients certainesters of dicarboxylic, hydroxy dicarboxylic, and hydroxy carboxylicaliphatic acids, each ester having a total of six to fifteen carbonatoms. It is preferred to select a substance of this class which isrelatively non-volatile, or which has a boiling point above about 100C., and those substances which have but slight odor, or which possessnot unpleasant odors are most desirable.

In general, the esters of lactic, malic and adipic acids are preferred,and specific esters of these acids which are useful in making theimproved insect repellents are: ethylene glycol monoethyl ether lactate,tetrahydrofurfuryl lactate, benzyl lactate, diethyl dl-malate, dibutyll-malate, di-

butyl dl-malate, diethyl adipate, dipropyl adipate, dibutyl adipate, anddi(ethylene glycol monoethyl ether) adipate.

Insect repellent compositions containing this class of substancesgenerally, and dibutyl dimalate, ethylene glycol monoethyl etherlactate, and diethyl adipate specifically are the subject of myco-pending application'Serial Number 211,819, filed June 4, 1938.

This application is specifically directed to insect repellentcompositions containing dibutyl l-malate, diethyl dl-malate, benzyllactate, and tetrahydrofurfuryl lactate.

The advantages realized by employing the above compounds as repellentsinclude the provision of effective repellency against such insects asmosquitoes, house flies, stable flies, black fliesand fleas with aminimum of discomfort to the user. The substances named are allrelativelyv non-volatile liquids, and are therefore lasting repellents.Unlike many other repellents, notably essential oils such as citronella,these ma terials are almost odorless, and,- if desired, suitableperfumes may be incorporated. Preparations containing these materialsmay be placed directly in contact with the skin or clothing since theyhave, in general, no irritating effect upon the skin or deleteriousaction onfabrics. n sensitive skin a slight reddening is sometimescaused by the malic acid esters, and the adipic acid esters may producea momentary smarting sensation. This .is particularly true if the estersare applied undiluted. These compounds are not greasy or oily in nature,and they may be easily washed ofi. Because of theirsolvent nature theymay have a cleansing eflect on the skin, and they may tend to soften ordissolve paints and cosmetics with which the repellent comes in contact.

As a rule, it is desirable to incorporate small amounts of certain inertmaterials, such as vege-' table or mineral oils, particularly corn oil,with.

the repellent because on a dry type of skin these repellents sometimestend to form a dry white layer two or three hours after application.While this is in no way harmful, it is undesirable from.

the viewpoint of appearance.

Tests made against salt marsh mosquitoes (Aedes sollicitans) have shownthat these compounds are on an average from two to ten times aseffective repellents as oil of citronella, or from ten to fifteen timesas effective as pine oil or the like. In particular, dibutyl dl-malatehas shown an effective repellency of at least fiveto ten times that ofoil of citronella.

Other insects, such as stable flies (Stomozys calcitrans) and strawberryor deer flies (Chm/sop spp.) have been repelled, but against such fliesthe period of repellency is considerably shorter than againstmosquitoes. The species of insect against which protection is soughtalso influences results. The house mosquito (C'. pipiens) bites only atdusk and at night and is relatively easy to repel as compared to thewoodland mosquito (A. vexans), which bites during the day as well.

7 From observations in the field, the salt water marsh mosquitoes (A.sollicitans, A. c'antator and A. taeniorhunchus) are the fiercest bitersand most difficult to repel. They are also active during the day as wellas at night.

Although the better repellents are relatively non-volatile (boilingpoints usually being above about C.) some degree of volatility isnecessary to keep the insects-particularly mosquitoes-away from treatedparts.

The compounds described may be applied, as such, to surfaces from whichit is desired to repel the insect pests. They may also be applied asingredients of lotions compounded with volatile diluents, such asethanol, or less volatile materials, such as glycerol, or they may bemixed with one another. In general, dilution with inert materialsreduces the effect of repellency of the compound. The repellent may beapplied in combinations with various oily carriers, including vegetableoils, such as castor oil and peanut oil, and certain mineral oils.Unguents or creams containing the repellents, as well as powders orcarriers of like nature may be effectively used. In any of the different.modes of application, it will be understood that mixtures or blends ofthe individual repellents may March 11, 1936, with which it wascopending.

I claim:

1. An insect repellent composition which contains one of the groupconsisting of dibutyl l-malate, diethyl dl-malate, benzyl lactate, andtetrahydrofuri'uryl lactate.

2. An insect repellent composition which consists of an inert diluentand an active repellent ingredient from the group consisting of dibutyll-malate, diethyl dl-malate, benzyl lactate and tetrahydrofurfuryllactate. v

3. An insect repellent composition which consists of an inert diluentand a repellent; said diluent containing an oil; and said repellentbeing from the group consisting .of dibutyl l-malate, diethyl dl-malate,benzyl lactate, and tetrahydrofuriuryl lactate.

4. An insect'repellent composition which consists of an inert diluentand a repellent; said diluent containing a. vegetable oil; and saidrepellent being from the group consisting of dibutyl l-malate', diethyldl-malate, benzyl lactate,

and tetrahydrofurfuryl lactate.

5. An insect repellent composition which contains diethyl dl-malate.

6. An insect repellent composition which contains tetrahydrofurfuryllactates.

7. An insect repellent composition which contains benzyl lactate.

PHILIP GRANE'I'I.

. CERTIFICATE OF CORRECTION. Patent No. 2,27h,267. February 21;, 19!;2.

PHILIP GRANETT.

It is hereby-certified that errorappears in the printed specification ofthe above numbered patent requiring correction as foliows:-Page 2, sec--0nd column, line 25, claim 6, for the word "lactatee" read---'lactate--; and that the said Letters Patent should be read with thiscorrection therein that the same may conform to the record of thecaseinthe Patent Office.

Signed andsealed this 21st day of April, A. D. 1911.2.

. Henry Van Aredale,-- (Seal) Acting Commissioner of Patents.

